What eats purple sea snails?

Answer 1

Ianthina

Any gastropod of the genus Ianthina, of which various species are found living in mid ocean; -- called also purple shell, and violet snail. [Written also janthina.] They are also known as whelks. Note: It floats at the surface by means of a raft, which it constructs by forming and uniting together air bubbles of hardened mucus. The Tyrian purple of the ancients was obtained in part from mollusks of this genus.

http://www.answers.com/topic/ianthina-1 Whelk This member of the gastropod branch of the mollusk family is a large marine snail. It has a beautiful spiraled shell and a rather tough but flavorful footlike muscle. Although the waved whelk is found along America's northern Atlantic coast, it has never gained wide popularity in the United States. Knobbed whelks and channeled whelks are also marketed in the States. Fresh whelks are generally available in the spring and fall. They're also available cooked, preserved in vinegar and canned. Because of their lack of popularity, whelks may be difficult to find except in Chinese or Italian markets or specialty food stores. Whelk is naturally tough and must usually be tenderized by pounding. It benefits from brief, gentle cooking. The Italians refer to whelk as scungilli, and the famous scungilli marinara is a garlicky dish of whelk cooked in a tomato sauce flavored with basil, oregano and hot pepper seeds. A 100-g portion of flesh (670g in the shell) is a rich source of protein, niacin, vitamin B12, and iron. http://www.answers.com/topic/whelk